Often no right or wrong answer (David Gibson)

David Gibson

As a hospital admissions pharmacist many of the patients I see have some degree of renal impairment. When prescribing in acute care, the accurate estimation of kidney function is a frequent consideration. For the majority of patients I still use the Cockcroft and Gault equation because it provides an adequate estimation of renal function even for those patients at the extremes of body weight.

Difficulties can arise when treating the elderly, frail patient whose creatinine is, at first glance, within normal range. We see an 86-year-old man on the post-take ward round and he is diagnosed with pneumonia. We make the decision that he has a severe pneumonia that needs to be treated aggressively. The trust antibiotic formulary recommends intravenous co-amoxiclav — but before I prescribe this I decide to check his creatinine clearance. Because of his age and low body weight this turns out to be 29.5ml/min despite his creatinine level being within the normal range.

The product information for co-amoxiclav recommends reducing the dose to 600mg bd. This feels too low and I opt for the dose recommended in the ‘Renal Drug Handbook’ of 1.2g bd. This achieves the balance I require of treating the pneumonia aggressively while limiting the risk of toxicity.

Our patient also requires enoxaparin for thromboprophylaxis. This is a simpler decision and I prescribe 20mg daily. His blood pressure is low and this makes withholding his angiotensin-converting enzyme inhibitor an easy choice. Checking his digoxin level will rule out toxicity, due to accumulation, as the cause of his confusion.I then just need to reduce his allopurinol dose to 100mg once daily and I am happy.

I then consider what will happen if his renal function improves as his condition does. His creatinine clearance is likely to rise above 30ml/min and all the careful adjustment of his drug regimen will need to be reviewed to reflect his changing clinical condition. I therefore ensure that as part of my prescribing I include a clear plan of how often I want his renal function to be monitored and what to do if this improves.

It is not just renal impairment that will provide these grey areas where difficult choices need to be made. A pharmacist prescriber needs to be able to apply clinical judgement to situations where there is often no right or wrong answer.

As I become more experienced as a prescriber I feel more able to deal with complex patients and actually enjoy the challenge of weighing up the evidence to achieve the desired outcomes.

David Gibson is senior clinical pharmacist (medical admissions) at Darlington Memorial Hospital